Size-dependent Optical Response of Magneto-plasmonic Core-shell Nanoparticles

Functional properties tunability prospect of multi-layered and multi-metallic nanoparticles with respect to their emerging applications has always been the area of attraction. Magnetoplasmonic nanoparticles (MPNPs) present the possibility to exhibit their tuneable magnetic and optical properties with broad applications in magnetic resonance imaging (MRI), cancer therapy, photovoltaic solar cells, biological microscopy, optical imaging, and biosensing. Present studies found that the optical properties (absorption and scattering efficiencies) of MPNPs using Fe, Co and Ni as magnetic materials coated with single noble metal (Au or Ag) or double (both Au & Ag) coating layer, can be effectively tuned with the controlled size of core and shell layers. It is found that absorption and scattering LSPR peaks occur in Ultraviolet (UV) and visible region of EM for single core-shell MNP@Ag nanoparticles respectively. The absorption LSPR are found in the visible region, and scattering LSPR in NIR region and also get blue shifted for single core-shell of MNP@Au nanospheres. In case of double core-shell layers of MNP@Ag@Au nanoparticles, the absorption and scattering LSPR peaks show spectra in visible and NIR region of EM spectrum and the absorption LSPR peak shifts from visible to UV region and scattering LSPR are found in NIR region with broadening peaks of EM spectrum. It is concluded that the LSPR peak depends upon the thickness of the shell, size of core and material. The shifting of optical peaks towards the longer wavelengths depends on gold shell thickness whereas optical efficiencies depend on silver (as core or shell) thickness.